A conventional acceleration slip control device for a motor vehicle is designed to begin to control acceleration slip when the speed of a driving wheel has exceeded a reference speed, or when the slip ratio of the driving wheels has exceeded a reference slip ratio. In this acceleration slip control, the opening of the throttle valve is controlled by a feedback control system so that for example the slip ratio of the driving wheels may correspond to a target slip ratio.
The acceleration slip control device in conventional use for motor vehicles, however, has such a problem that if the acceleration slip control is started after the driving wheel speed has exceeded a reference speed, there takes place a delay time between the throttle valve opening and a target opening, resulting in a lowered initial response property of the acceleration slip control.
That is, if throttle valve operation starts upon the detection of an acceleration slip, the driving wheels slip excessively during the period of time delay until the throttle valve opening agrees with the target opening, resulting in an insufficient acceleration performance.
It is, therefore, an object of the present invention to provide an acceleration slip control device for motor vehicles which is capable of realizing a good acceleration performance by presetting the initial throttle valve opening suitable to restrain the acceleration slip in accordance with a predicted occurrence of the acceleration slip.